Home | Error Codes | 7e8 and 7e9 Engine Code: A Detailed Overview

7e8 and 7e9 Engine Code: A Detailed Overview

March 20, 2024 | Victor Lukasso

The 7e8 and 7e9 engine codes are among the complex error codes that might be shown on your OBD-II scanner.

The 7e8 engine code is often accompanied by the 7e9 error code, which is used to signify an issue in the engine data stream.

A 7e8 error code signifies air pressure loss for the emission control system, which can also be likened to an issue with the engine power train. The 7e9 code indicates a problem in the engine transmission. In summary, 7e8 denotes an issue(s) in the engine, and 7e9 means there’s an issue in the transmission.

This article will extensively discuss the 7e8 and 7e9 engine codes, including their meaning, causes, and fixes.


7e8 and 7e9 Engine Code

Even though the two engine codes seem to relate to the engine control module, they differ.

The 7e8 engine code indicates a problem with the engine powertrain. Meanwhile, the 7e9 suggests a problem with the transmission powertrain.

Let me explain…

What is Engine Code 7e8?

Error code 7e8 is a diagnostic trouble code that indicates air or fuel intake into the engine control system, thereby leading to a loss of air pressure in your vehicle’s evaporative emission control system.

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The engine generates its power from the internal combustion cycle in the cylinder, and the combustion chamber uses petrol mixtures and trapped air to create heat and produce a spark, which in turn moves the car.

Depending on the model of your cylinder head, uncompressed air or unburnt fuel can get into the control system and reduce air pressure.

Some car models, such as the Chevy and GMC Sierra, will also show this code if the knock sensor detects a vibration from the engine.

This error code is a minor issue and may not cause any problems because it’s often resolved in minutes, and a lousy sensor might be responsible for showing the code – which means there was never a problem.

If you doubt the cause of the error code, you can employ a multiple-purpose OBD-II scanner for this purpose. This problem is common in cars such as Kia, Jeep, Nissan, Hyundai, Subaru, Volkswagen, Mercedes, and even BMW.

It’ll reveal the reason(s) why your check engine light is turned on and provide possible fixes for you.

What is Engine Code 7e9?

The 7e9 error code indicates an issue with the TMS (transmission management system), and the engine might lose power soon.

Remember, the 7e8 engine code is associated with the air and fuel mixture entering the combustion system. Likewise, the 7e9 engine code is shown alongside to show a fuel leak, overheating, or slipping in the engine.

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This code is a major one and should be resolved on time because it could result in stalling, misfiring, or an unresponsive engine.

If you doubt the cause of the error code, you can employ a multiple-purpose OBD-II scanner to help check the code.

It’ll reveal the reason(s) why your check engine light is turned on (5-digit code) and provide possible fixes for you.

7e8 Engine Code – Causes

Here are possible reasons why the 7e8 error code will be displayed on your check engine light.

  • Leaking fuel vapor lines
  • Disconnected vapor lines
  • Damaged Canister
  • Bad Canister Close Valve
  • Bad fuel tank pressure valve
  • Unplugged fuel vapor line
  • Faulty pressure control solenoid valve
  • Bad fuel pump seal
  • A Bad fuel filler pipe
  • Bad fuel filler cap

That’s it for the causes of the 7e8 engine code Chevy.

How to Fix the 7e8 Engine Code

The 7e8 error code revolves around the air and fuel mixture entering the engine control system.

Here are some DIY tips you can implement to fix the error code.

  • Get a fuel cap replacement
  • Run an EVAP leakage test on your car
  • Perform a smoke test on your EVAP system
  • Check if your fuel level is between 15% – 80%
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You can now clear the codes on your OBD-II scanner and perform a new test. The codes should clear off by now.

Also, endeavor to perform an EVAP test on your car after driving for 10,000 miles to prevent poor gas mileage and the $7e8 engine code.

You can take your car to a professional mechanic if the engine code persists after initiating any of the above fixes.

How to Fix the 7e9 Engine Code

The 7e9 code can be curbed by regular maintenance of your vehicle. Transmission issues usually indicate changing your driving habits or ensuring your car’s engine is always standard.

You can always take your car to a mechanic’s workshop for proper servicing and maintenance.

They’ll use an OBD-II scanner to scan out all the necessary troubles on the car and fix them accordingly.

Clear the scanner and see the code disappear from your check engine light.

Difference between 7e8 and 7e9 Engine Code

7e8 Engine Code

7e9 Engine Code 

Faults in the Engine Powertrain Faults in the Transmission powertrain
A minor issue A major issue
May not show any symptoms Stalling, misfiring, or unresponsive engine
Fixes are often DIY The service of a professional mechanic is needed


> 7e8 Engine Code: Meaning and How to Fix

$7e8 Engine Code: A Detailed Overview

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Meet Victor Lukasso, the owner of V. Auto Basics. Through this blog, Victor Provides Insights on the latest tips, maintenance, repair, and techniques in the automotive world.